The objective of this study is to determine, from a tumor cell kinetic viewpoint, the optimum timing to administer chemotherapy following ablative or near-ablative surgery. Based upon the information that surgery perturbs the cell kinetics of remaining tumor, as described previously by us and other investigators, we intend to determine the time sequence of cell kinetic changes following removal of varing quantities of tumor in several different animal tumor models. The models picked for this study are the spontaneous mammary tumor of the C3H mouse, a first gerneration transplant of the above tumor into a C3H mouse, and the multi-generation transplantable S-102F rapidly growing tumor in the C3H mouse. Thus, we will look at breast tumors of similar origin, in similar animals, but that have different proliferative potentials. Following basic studies of a temporal nature we will look at metastases of some of these tumors, as well as at the tumors following perturbing influences such as prior radiation, chemotherapy and nutritional alterations. On the basis of these results we will look at the effects of chemotherapy given at various times after surgery to try and confirm the hypothesis that treatment, temporally designed by virtue of tumor cell kinetic measurements, will result in improved results of delayed tumor regrowth.